# GRE

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1. area of triangle
1/2 base x height
2. pythagorean theorem

only for right triangles
a2 + b2 = c2
3. right triangle ratios

(4)
• 3:4:5
• 5:12:13
• s : s : s/2
• s : s/3 : 2s
4. area of square

(2)
• s2
• 1/2 d2 d=diagonal
5. area of rhombus, 4 equal sides, 4 angles that aren't necessary right angles
1/2 d1 d2
6. area of parallelogram

2 opposite and equal pairs of sides
base x height
7. area of rapezoid
1/2 (b1 + b2) x h
8. total interior angle
(n-2) 180

n=number of sides
9. average measure of one angle in polygon
(n-2)180 / n
10. volume of polygon
area of the base x height
11. volume of a cylinder
(pie r2) height
12. total surface area of a cube
6e2
13. total surface area of rectangular solid
2(l w) + 2 (w h) + 2 (h l)
14. total surface area of a cylinder
(circumference x height) + 2(pie r2)
15. distance between 2 points
/ (x2 - x1)2 + (y2 - y1)2
16. circumference of circle
2pie r

pie d
17. area of circle
pie r2
18. length of an arc
• 1. find the circumference of the circle (2pie r, pie d)
• 2. put the degree measure* of the arc over 360, reduce fraction
• 3. multiply circumference by the fraction
19. area of a sector
• 1. find area of the circle (r2)
• 2 . put degree measure* of sector over 360, reduce
• 3. multiply the area by the fraction
20. equations for FOIL
• (a+b)2 = a2 + 2ab + b2
• (a-b)2 = a2 - 2ab + b2
• (a-b)(a+b) = a2 - b2
21. find probability
number of possible desired outcomes/ number of total possible outcomes
22. find distance
• distance = rate x time
• time = distance/ rate
• etc
23. average
sum/ number of terms
24. average common sense way

average is 90
numbers: 89, 88, 93, 92 90
-1, -2, +3, +2

• = +2
• need to get 88 to get average (subtract the number extra or add number needed)
25. percent increase or decrease
number increase or decrease/ original whole
26. interest problems
• PRTI
• Principal x Rate x Time = Interest

• principal:amount money begin with
• rate: interest rate you're earning on the money, expressed as a decimal
• time: amt of time (years) money left in account
• interest: amt of interest earn on the investment
27. work
time put in/ capacity, time to do the whole job
 Author: chellen12 ID: 51723 Card Set: GRE Updated: 2010-11-26 05:35:30 Tags: equations Folders: Description: math equations Show Answers: